I would like to raise the left Tick over the x-axis so it doesn't clip into the graph. However If I add a second "Extra x ticks" definition the first definition gets overwritten. How can I achieve an individual tickstyle for each tick. This question is related however it doesn't work for three different tickstyles. (See comments in the answer)
\documentclass{article}
\usepackage{multirow}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{pgfplots}
\begin{document}
\begin{figure}[tb]
\begin{tikzpicture}[baseline] \begin{axis}[
ylabel style={rotate=-90},
xtick = 0,
ytick = 0,
xtick style={draw=none},
xmin = -5,
xmax = 5,
ylabel={$I$},
xlabel={$U$},
extra x ticks = {-2,2},
extra x tick labels = {$ -E_{ \text{t}} $, $ E_{ \text{t2}} $},
extra x tick style = { grid = major },
axis y line=middle,
axis x line=middle,
]
\addplot[blue,samples=21]
coordinates {
(-5,-5)
(-2,-1)
(2,1)
(5,5)
};
\end{axis}%
\end{tikzpicture}%
\end{figure}
\end{document}